This application claims priority to Japanese Patent Application No. 287424/1999, filed Oct. 7, 1999, which is incorporated herein by reference.
This invention relates to a catalyst for hydrotreating and a process for hydrotreating hydrocarbon oils using the same, more particularly to the multi-component solid catalyst with a hydrogenation-active component dispersed uniformly in a matrix of refractory, inorganic oxide, and the process for hydro-treating hydrocarbon oils using the same.
Various types of catalysts have been proposed for hydrotreating hydrocarbon oils, e.g., those with one or more hydrogenation-active components carried by a refractory inorganic oxide (e.g., alumina, silica, magnesia and zirconia), and the hydrogenation-active component is selected from the group consisting of the group 6A elements (e.g., molybdenum, tungsten and chromium) and the group 8 elements (e.g., cobalt and nickel).
One of the widely used methods for producing these catalysts is impregnation, in which a carrier is impregnated with an aqueous solution of a group 6A element and group 8 element, dried and calcined. One of the disadvantages involved in the impregnation method is difficulty in dispersing the active component highly uniformly, because it is highly mobile during the catalyst production process from adsorption or precipitation to completion of drying. This mobility comes from the weak bond between the active component and carrier, because the carrier is impregnated, after it is prepared, with a solution of the active component, with the result that it is merely adsorbed or precipitated on the carrier.
Other disadvantages are limited content of the active component and difficulty in controlling the content in an optimum range. The active component is immobilized on the already prepared carrier, by which is meant that content of the active component tends to be limited by total pore volume of the carrier.
The conventional catalyst, therefore, tends to suffer lack of homogeneity and decreased number of active sites, when content of the active component is optimized to enhance catalyst hydrotreating activity. This tends to limit its activity. Therefore, new techniques for the catalysts of high homogeneity and activity have been increasingly in demand. As one of the attempts to realize such a catalyst, Japanese Laid-open Patent Application No. 83603/1986 discloses a method for producing a homogeneous, amorphous complex metal oxide. This method, however, involves several disadvantages. First, satisfying the amorphous condition tends to limit content of the hydrogenation-active component, and hence catalyst activity for hydrotreating. A carrier containing crystalline compound, e.g., xe2x80x94Al2O3, which has an effective function as the carrier for hydrotreating catalyst is no longer used for this method. An amorphous metal oxide is unstable and low in mechanical strength, and hence unsuitable for a commercial catalyst which is required to exhibit long serviceability.
Recently, reduction of sulfur content of gas oil is strongly required for environmental reasons, especially by deep desulfurization of stocks of high sulfur contents, e.g., light gas oil (LGO), vacuum gas oil (VGO) and cracked gas oil. In particular, sulfur content of diesel fuel oil is required to be reduced to 0.05 wt. % or lower. The techniques to achieve the required desulfurization level have been studied from wide angles, and it is now considered that whether this is achieved or not largely depends on whether sulfur compounds difficult to remove, e.g., 4-methyl dibenzothiophene and 4-6-dimethyl dibenzothiophene, are efficiently desulfurized. Development of catalysts of higher activity is essential also viewed from the above point.
It would be desirable to provide a high-activity hydrotreating catalyst, with a hydrogenation-active component highly dispersed, high in homogeneity and containing a crystalline component, which is also high in desulfurization activity for hydrotreating hydrocarbon oil, and also excellent in activity for, e.g., denitrogenation, dearomatization and cracking and which can treat diversified types of hydrocarbon oils, e.g., hydrodesulfurization, hydrodenitrogenation, hydrodearomatization, hydroisomerization, hydrocracking, hydrodewaxing, hydrodemetallization, in particular deep hydrodesulfurization of a diesel fuel fraction.
The inventors of the present invention have found, after having conducted extensive studies, that the catalyst comprising a refractory inorganic oxide matrix dispersed with a hydrogenation-active component, high in homogeneity and containing a crystalline component shows high activity for hydrotreating (e.g., hydrodesulftuizing) a hydrocarbon oil.
The present invention provides a hydrotreating catalyst containing a crystalline component comprising a refractory inorganic oxide matrix dispersed with a hydrogenation-active component,
said hydrogenation-active component comprising at least one active component (A) selected from group 6A elements, and/or at least one active component (B) selected from the group 8 elements, wherein
(1) total content of said hydrogenation-active component is 0.02 moles to 0.4 moles per mole of all of the elements that constitute the catalyst,
(2) of said hydrogenation-active component, any one, when present at 0.002 mol/mol or more, satisfies the following relationship (1), established by the electron probe microanalysis (xe2x80x9cEPMAxe2x80x9d) line analysis:
Nmaxxe2x88x92Nminxe2x89xa62xc3x97[3xc3x97(N0)0.5+0.2xc3x97N0]xe2x80x83xe2x80x83(1)
(Nmax, Nmin and N0 are the maximum, minimum and average contents of the hydrogenation-active component, determined by the EPMA line analysis), or following relationship (2), established by the EPMA plane analysis:
0.8xe2x89xa6S parameter less than 1, 0.8xe2x89xa6P parameter less than 1xe2x80x83xe2x80x83(2)
(S parameter and P parameter are an index for size uniformity and distribution of the active component particles, respectively, determined by the EPMA plane analysis), and
(3) one or more diffraction lines relevant to crystalline component are observed by powder X-ray diffraction analysis.
The present invention also provides a process for hydrotreating a hydrocarbon oil, where the oil is brought into contact with hydrogen under hydrotreating conditions in the presence of the above hydrotreating catalyst.